Tidal currents in the northwestern Adriatic: High-frequency radio observations and numerical model predictions

A 2-year deployment of high-frequency radio current meters along the Italian coast of the northwestern Adriatic is used to characterize the surface tidal currents. In the middle of the basin, the M2 and K1 currents oscillate along the basin axis, but become more circular toward the Italian coast. Comparisons with a 3-D finite-element nonlinear numerical model of the tides show a good agreement for phases in the middle of the basin, although modeled currents amplitudes are overestimated. However, modeled phases lag observed phases by up to 50 (1.7 hours) for M2 and 100 (6.7 hours) for K1, and modeled amplitudes are underestimated, in a 10–20 km wide strip along the Italian coast. This shallow (< 30 m deep) region is stratified by low-salinity surface water from the Po, and laterally sheared by the Western Adriatic Current, both absent from the model but possibly affecting tidal propagation. The model may also incompletely parameterize the combined effects of bottom friction and vertical mixing of momentum.